2. The Chemistry of Life Building Blocks of Matter: Atoms + + + + + + + - - - - -- - - +

3. The Chemistry of Life Life depends on chemistry. When you eat food or exhale oxygen, your body uses these materials in chemical reactions that keep you alive. Living things are made from chemical compounds.

4. 3 Matter: –Matter is defined as anything that has mass and occupies space –Matter exists in three states: solid, liquid, and gas

5. Atoms Smallest possible unit into which matter can be divided, while still maintaining its properties. Made up of: –protons –neutrons –electrons The solar system is commonly used as an analogy to describe the structure of an atom For example, what is the smallest possible unit into which a long essay can be divided and still have some meaning? + - + + + - - - - +

6. ATOMS Atoms are the basic unit of matter Comes from the Greek word “atomos” which means unable to cut. From Greek philosopher Democritus who wondered if you break chalk would it change it to something else (all science starts with a QUESTION) Atoms are extremely small. Subatomic particles are even smaller.

7. Atoms are so small that… it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen. if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping-pong ball a human hair is about 1 million carbon atoms wide. a typical human cell contains roughly 1 trillion atoms. a speck of dust might contain 3x10 12 (3 trillion) atoms. it would take you around 500 years to count the number of atoms in a grain of salt. www.deckersfoods.com C-C-C-C-C-… + 999,995 more 1 trillion atoms . Is made of approximately 3 trillion atoms Just one of these grains

8. Protons (+) Positively charged particles Help make up the nucleus of the atom Help identify the atom (could be considered an atom ’ s DNA) Equal to the atomic number of the atom Contribute to the atomic mass Equal to the number of electrons + + + + + + + + - - - - -- - - +

9. Neutrons Neutral particles; have no electric charge Help make up the nucleus of the atom Contribute to the atomic mass + + + + + + + - - - - -- - - +

10. Electrons (-) Negatively charged particles Found outside the nucleus of the atom, in the electron orbits/levels; each orbit/level can hold a maximum number of electrons ( 1 st = 2, 2 nd = 8, 3 rd = 8 or 18, etc…) Move so rapidly around the nucleus that they create an electron cloud Mass is insignificant when compared to protons and neutrons Equal to the number of protons Involved in the formation of chemical bonds - + + + + + + + - - - - -- - - +

11. The Atom ’ s “ Center ” Protons and neutrons are grouped together to form the “ center ” or nucleus of an atom. - + + + Notice that the electrons are not apart of the nucleus - -

12. Sub-Atomic Particles Weight Comparison (protons, neutrons, electrons) Neutron = 1.6749286 x10 -27 kg Proton = 1.6726231 x10 -27 kg Electron = 9.1093897 x10 -31 kg + - + ---- --- -- -- - - - - - - ----- --- -- -- - - - - - - 1836 electrons = 1 proton1839 electrons = 1 neutron How do you think the mass of a neutron compares to that of a proton? 1 neutron ≈ 1 proton

13. ELEMENTS An elements is a pure substance that consists entirely of one type of atom. All matter (both living and non-living) is composed of 92 naturally-occurring elements 98% of body weight of organisms are primarily composed of six elements (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur— acronym CHNOPS) make up 98% of the body weight of organisms.

14. 25 Elements are essential to life C, H, N, O, P, S: 96% of the weight of the human body

15. 14 Composition of Earth’s Crust versus Organisms 60 40 20 0 FeCaKSPSiAlMgNaONCH Earth’s crust organisms Element Percent by Weight Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Gunter Ziesler/Peter Arnold, Inc.

16. https://www.youtube.com/watch ?v=im8tmwTnnhM

17. Each element consists of one kind of atom Atom: smallest unit of matter that retains the properties of an element Fig. 2.02 (a) Hydrogen atom (b) Carbon atom(c) Oxygen atom Proton NeutronElectron Atomic nucleus First shell Second shell

18. Hydrogen (H) Atom Notice the one electron in the first orbital + - Even though there are no neutrons present, Hydrogen is still considered an atom + - = 1 = 0 = 1 How many more electrons can fit in the 1 st orbital/ level?

19. Oxygen (O) Atom Notice the two electrons in the first orbital/level and the six in the second + + + + + + + - - - - - - - - + + - = 8 How many more electrons can fit in the 2 nd orbital/ level?

20. Sodium (Na) Atom Notice the two electrons in the first orbital/level, eight in the second, and one in the third + + + + + + + - - - - - - - - + - - - + - = 11 = 12 = 11 How many more electrons can fit in the 3 rd orbital/ level?

21. Atomic Number The number of protons in the nucleus of an atom + + + - - - What would be the atomic number of this atom?

22. Atomic Mass Number The total number of protons and neutrons in an atom ’ s nucleus Expressed in Atomic Mass Units (amu) –Each proton or neutron has a mass of 1 amu + + + - - - What would be the mass number of this atom? +  3 3  4 4 3 protons + 4 neutrons = a mass number of 7 amu Why did we not account for the electrons when calculating the mass number?

23. 22 Atomic Symbols Each element is represented by one or two letters to give them a unique atomic symbol –H–H = hydrogen, Na = Sodium, C = Carbon Each atom has its own specific mass (atomic mass) Atomic mass of an atom depends on the presence of subatomic particles –A–Atomic number = proton number; –A–Atomic mass or mass number = protons and neutrons

24. Remember: Atomic Mass = protons + neutrons To get neutron # = AM – AN OR AM – P# To get electron # = Same as Atomic Number but negative sign

25. Building Atoms Draw diagrams of the following atoms, and determine their atomic number and atomic mass number. AtomsProtonsNeutronsElectrons Carbon666 Beryllium454 Oxygen888 Lithium343 Sodium111211

26. 25 Periodic Table Elements grouped in periodic table based on characteristics –V–Vertical columns = groups; chemically similar –H–Horizontal rows = periods; larger and larger Atomic mass increases as you move down a group or across a period.

27. 26 Periodic Table Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Periods Groups 19 39.10 K 20 40.08 Ca 31 69.72 Ga 32 72.59 Ge 33 74.92 As 34 78.96 Se 35 79.90 Br 36 83.60 Kr 11 22.99 Na 12 24.31 Mg 13 26.98 Al 14 28.09 Si 15 30.97 P 16 32.07 S 17 35.45 Cl 18 39.95 Ar 3 6.941 Li 4 9.012 Be 5 10.81 B 6 12.01 C 7 14.01 N 8 16.00 O 9 19.00 F 10 20.18 Ne I 1 1.008 H atomic number atomic symbol 2 4.003 He VIII atomic mass IIIIIIVVVIVII

28. Periodic table of the elements

29. 28 Isotopes Isotopes: –A–Atoms of the same element with a differing numbers of neutrons (and therefore have different atomic masses). e.g. see carbon below Some isotopes spontaneously decay Radioactive Give off energy in the form of rays and subatomic particles Can be used as tracers Mutagenic – Can cause cancer 12 6 Carbon 12 C 13 6 Carbon 13 C 14 6 Carbon 14 C

30. FORCES IN THE ATOM Gravitational Force Electromagnetic Force Strong Force Weak Force

31. Gravitational Force The force of attraction of objects due to their masses The amount of gravity between objects depends on their masses and the distance between them Do you think this force plays a significant role in holding the atom together?

32. Electromagnetic Force The force that results from the repulsion of like charges and the attraction of opposites The force that holds the electrons around the nucleus - + + + -- Notice how the particles with the same charge move apart and the particles with different charges move together. Why are neutrons not pictured above?

33. Strong Force The force that holds the atomic nucleus together The force that counteracts the electromagnetic force If you need help remembering strong force, just think of… + + + + Notice how the electromagnetic force causes the protons to repel each other but, the strong force holds them together. Would an atom have a nucleus if the strong force did not exist?

34. - n Weak Force This force plays a key role in the possible change of sub-atomic particles. –For example, a neutron can change into a proton(+) and an electron(-) The force responsible for radioactive decay. –Radioactive decay  process in which the nucleus of a radioactive (unstable) atom releases nuclear radiation. + If you need help remembering weak force, just think of… Notice how the original particle changes to something new.

35. Isotopes Atoms that have the same number of protons, but have different numbers of neutrons Examples + - + - + - Hydrogen (Protium)Hydrogen (Deuterium)Hydrogen (Tritium) Notice that each of these atoms have one proton; therefore they are all types of hydrogen. They just have a different mass number (# of neutrons).

36. Atomic Mass The weighted average of the masses of all the naturally occurring isotopes of an element The average considers the percent abundance of each isotope in nature Found on the periodic table of elements Example + - + - + - Hydrogen (Protium) Mass # = 1 amu Hydrogen (Deuterium) Mass # = 2 amu Hydrogen (Tritium) Mass # = 3 amu If you simply average the three, 2 amu (1 amu + 2 amu + 3 amu/3) would be the atomic mass, but since 99.9% of the Hydrogen is Protium, the atomic mass is around 1 amu (.999 x 1 amu) What would be the atomic mass (≈) of Hydrogen if these three isotopes were found in the following percentages (99.9, 0.015, 0) respectively?

37. Symbol = O 2+ Ion Charged particle that typically results from a loss or gain of electrons Two types: –Anion = negatively charged particle –Cation = positively charged particle + + + + + + + - - - - - - - - + - Now that this atom of oxygen just gained an electron, it is no longer neutral or an atom. It is now considered an ion (anion). This ion has more electrons (9) than protons (8). + - = 8 96 Symbol = O 1- Now that three electrons were lost, the number of electrons (6) and protons (8) is still unbalanced; therefore, it is still an ion, but now it is specifically referred to as a cation. Currently, this atom of oxygen is neutral because it has an equal number of electrons (8) and protons (8). Symbol = O

38. Building Ions Using the whiteboard and the proton, neutron, and electron pieces, build the following ions, and determine their atomic and mass numbers. IonsProtonsNeutronsElectrons Carbon (C³¯)669 Hydrogen (H¹+)100 Oxygen (O²¯)8810 Lithium (Li³+)340 Sodium (Na¹¯)1112 Be aware that the atomic and mass numbers are not impacted by the loss or gain of electrons.